1. Field of the Invention
The present invention relates to a TV, and more particularly, to a combined TV receiver which can receive and process an analog broadcasting signal as well as a digital broadcasting signal.
2. Background of the Related Art
The TV receiver is an appliance for decoding a broadcasting signal transmitted from a broadcasting station into an image signal and presenting image information to TV watchers. There are different standards of TV systems depending on scanning lines, frames per second, modulation type, channel bandwidth, video signal bandwidth, and audio channel modulation of a broadcasting signal transmitted from the broadcasting station, inclusive of the NTSC(National Television System Committee), PAL(Phase Alternation by Line), SECAM(Sequential Couleur a Memoire). The NTSC system is a standard system of a broadcasting signal having 525 scanning lines and transmitting 30 frames per second used in the north America, Japan and Korea. The NTSC system is compatible with black and white TV and has a simple driving circuit compared to other systems. The PAL system is a standard system of a broadcasting signal used in most European countries except some eastern European countries starting from France, in which a phase of one of two color difference signals are inverted at every scanning line in modulation. Though the PAL system has a somewhat poor compatibility with a black and white TV, a video signal of the PAL system is less influenced by a phase distortion caused by recording or transmission. The SECAM system is a standard system of a broadcasting signal developed in France and used in France, the old soviet union, east Europe and some African countries, in which a color subcarrier is frequency modulated and overlapped with a luminance signal while the two color difference signals are cut off in a sequence before transmission. Though the SECAM system is advantageous in small amplitude and phase distortions during transmission, a vertical resolution is poor.
FIG. 1 illustrates a block diagram of a related art analog TV receiver circuit schematically, of which operation will be explained. A tuning data is received at a tuner 1. Then, a VIF(Video Intermediate Frequency) 2 provides a video signal, of which synchronizing signal is detected by a synchronizing signal detector 3. If a synchronizing signal is contained in the signal received from the antenna, the signal is an analog signal, if there is no synchronizing signal, the signal is not an analog signal. An analog broadcasting receiver determines the presence of a broadcasting signal according to existence of a synchronizing signal, and stores a channel number having a broadcasting signal in a memory.
In the meantime, there have been research and other efforts for replacing a related art analog transmission type TV system with a digital transmission type TV gradually as digital technologies and video and audio data compression and restoring technologies are developed. In such a digital terrestrial TV broadcasting transmission system, there is a system of the USA and a system of Europe. The USA system is a VSB transmission system in which a single carrier is used and the European system is a COFDM(Coded Orthogonal Frequency Division Multiplexing) transmission system in which multi carriers are used. Particularly, because the multi carriers are used, the COFDM system is strong against interference and ghost in multiple path channel and allows to construct an SFN(Single Frequency Network) which can make a wide band transmission in a signal frequency. Because the present carrier condition is sensed in the COFDM system for making a Viterbi decoding with reference to the channel condition, an interference between channels or a selective fading of a frequency affect system performance, seriously. Therefore, as shown in FIG. 2, in the COFDM system, a signal called pilot 5 having a predictable value is added at every fixed intervals both in frequency axis Nf and time axis Nt directions between carriers of data at a transmitter side before transmission, which is used in synchronization or equalizing required in reception for restoring data at a receiver side. Together with this, the related art COFDM transmitter side transmits TPS(Transmission Parameter Signaling) including information on various transmission modes, and the receiver side decodes the TPS for use in demodulation. That is, the COFDM system is characterized in the use of multi carrier intransmission as well as the addition of pilots before transmission for use at the receiver side.
FIGS. 3a and 3b illustrate reception blocks in a COFDM system. As shows, signals (t) received through an antenna is amplified as necessary through a transmission channel 11 and the amplification terminal 12. An amplification gain is controlled through an AGC(Auto Gain Controller) 16. The amplified signal is digitized at an A/D converter 13, provided to an I and Q demodulator 14, and converted into of an I signal and a Q signal. The I signal and Q signal are subjected to adjustment of frequencies and powers as they pass through an FFT(Fast Fourier Transformer) block 15 and an equalizer 31, and are restored into an original data as they pass through a demapper 32, deinterleavers 33 and 36 and FEC(Forward Error Corrector)(not shown). At first, the received data is provided to a course timing block 17 for being divided into an effective data interval and a guard interval. The course timing block 17 shifts data by one interval to obtain correlation between data, and provides the correlation to an FFT start window generator 18 for establishing an interval of the data appropriate for subjecting to FFT. After the I and Q composite signals are converted at the FFT block 15, TPS information is demodulated. The TPS demodulator 19 analyzes the pilot signals, and corrects frequency and time basis distortions of the received data using a result of the analysis, to decode a correct TPS signal. The pilot signals are detected from the signal subjected FFT at a scattered pilot extractor 20 and analyzed at an IFFT block 21 and a narrow and fine frequency controller 22 for obtaining a correct frequency band of the signal. The signal subjected to FFT is provided to a continual pilot extractor 23 for being frequency synchronized by which an error in a received frequency is corrected. And, the fine timing block 24 receives the data subjected to FFT and decodes a pilot signal in the data, for finding an exact timing of conversion of the FFT. The signal having frequency synchronized and frequency band corrected through the IFFT block 21, the narrow and fine frequency controller 22, and the fine timing block 24 is provided to the FFT block 15, again. The signal provided to the FFT block 24 is corrected for an error in a data carrier by hard or soft decision. The FFT 15 should be provided in a COFDM demodulating system for receiving an I signal and a Q signal and transform into frequency components. The signal transformed into the frequency components at the FFT is provided to a TPS(Transmission Parameter Signalling) decoder 19.
A memory 2 stores a signal from the FFT block 15 and provides the stored signal to the equalizer 31, and the equalizer 31 compensates for a distortion in a frequency response signal caused in a transmission channel. The demapper 32 receives both the signal having distortion compensated at the equalizer 31 and a TPS signal from the TPS decoder 19, and analyzes a mapped signal. The internal deinterleaver 33 subjects the signal analyzed at the demapper 32 to internal deinterleave, and provides the result to a Viterbi decoder 34. The Viterbi decoder 34 receives both 20 a signal from the internal deinterleaver 33 and the TPS signal, and subjects to viterbi decoding. An external deinterleaver 36 subjects the signal subjected to internal interleave to external interleave with reference to a synchronizing signal detected at a synchronizing signal detector 35. RS decoder 37 and a derandomizer 38 process the signal subjected to external interleave, for extracting a broadcasting signal of the channel the user selected. Also, the TPS decoder 19 receives a frequency component from the FFT block 15, analyzes a modulation type of the signal, and provides a result of the analysis to a processor(not shown). In this instance, different parameters are provided to the TPS decoder in succession until a right modulation type of the signal is analyzed. Accordingly, when the right modulation type of the signal is analyzed, the processor stores a channel of the signal having analyzed by the TPS decoder in an internal memory. If the TPS decoder can not detect the modulation type of the signal, the digital tuner receives information on a new channel number, and the aforementioned process is repeated. The TPS decoder is adapted to provide a right result only when the entire COFDM demodulator in the digital broadcasting receiver is operative regularly.
Most of the digital broadcasting signals provided to such digital TV receivers are based on the MPEG standards. Particularly, the MPEG-3 which is an MPEG standard for broadcasting and has all standards for system, audio and video established therein. For reference, the system standard No. in the MPEG-2 is ISO/IEC 13818-1, the video standard No. is ISO/WEC 13818-2, and the audio standard No. is ISO/IEC 13818-3.
A system and operation of a related art digital TV receiver based on the MPEG-2 standard will be explained with reference to FIG. 4.
Referring to FIG. 4, the related art digital TV receiver is provided with a tuner 100 for receiving a digital broadcasting signal, an IF converter 110 for subjecting the digital broadcasting signal received from the tuner 100 to frequency conversion to provide an intermediate frequency signal, a channel decoder 120 for detecting a pilot signal from the IF signal and decoding a lower frequency broadcasting signal, a TP parser 130 for parsing a TP signal from the lower frequency broadcasting signal to detect audio/video signals, audio/video decoders 140 and 150 for decoding the audio/video signals parsed at the TP parser, respectively, an audio signal converter 170 for converting a digital audio signal decoded at the audio decoder, a TV microprocessor 200 for controlling a TV system, a ROM 210 storing channels, programs, and the like, a RAM 220 for storing temporary data following operation of the TV microcomputer 200, an OSD processor 190 for processing OSD text, a switch unit 160 for selective forwarding the digital video signal decoded at the video decoder and the OSD text from the OSD processor 190, and a video signal encoder 180 for converting a video signal from the switch unit 160 into an image signal displayable on a TV or a monitor.
The tuner 100 receives and detects a QPSK(Quadrature Phase Shift Keying) signal or a QAM(Quadrature Amplitude Modulation) signal. The IF converter 110 receives a signal detected at the tuner and converts it into a signal of IF band, because the high frequency signal in a very high frequency band detected at the tuner can not be processed by a driving circuit of the digital TV, directly. The channel decoder, identical to the COFDM receiver block shown in FIGS. 3a and 3b, detects a pilot signal from the IF signal, decodes a baseband signal, converts the baseband signal into a digital signal, restores timing appropriate for the symbol rate, thereby correcting errors. The signal from the channel decoder 120 is a signal stream in the form of a transport stream packet in byte units. A transport signal stream as in MPEG-2 is a time-multiplexed signal stream named as a transport stream packet. The transport stream packet has a header at a beginning portion of the packet having a PID(Packet Identifier) number recorded therein. The PID number can be used as information which can demultiplex a time multiplexed signal. And, the PID number denotes a kind of the present packet, and, by analyzing the PID number, the present packet can be known as either a video packet, an audio packet, or program specific information. The video and audio standards in the MPEG-2 are standards on compressed video and audio signal streams. According to the MPEG-2 standards, all video signals, audio signals and program specific information signals are time-multiplexed, and transported as plural transport stream packets which can be identified with PID numbers.
The TP parser 130 parses a signal stream of such a transport stream packet form based on the PID number, and provides the result to respective decoders 140 and 150. That is, the TP parser 130 receives a transport signal stream through the tuner 100 and detects a PID number at a header of the signal stream. Thereby, the TP parser 130 parses a video signal stream, an audio signal stream and program specific information stream according to the PID numbers. Then, the TP parser 130 provides the video signal stream to the video decoder 150, the audio signal stream to the audio decoder 140, and the program specific information signal stream to the microcomputer 200.
The video decoder 150 decodes the video signal stream from the TP parser 130, and provides the result to the NTSC encoder 180. The video signal stream from the TP parser 130 is data compressed according to the MPEG-2 standards. According to this, the video decoder decompresses the compressed video signal stream, to restore an original digital video data. The audio decoder 140 decodes the audio signal stream from the TP parser 130, and provides to an audio digital to analog converter 170. The audio signal stream from the TP parser 130 is a data compressed according to the MPEG-1 standards. Therefore, the audio decoder 140 decompresses the compressed audio signal stream, to restore an original digital audio data. The audio digital to analog converter 170 converts digital audio data from the audio decoder 140 into an analog audio signal an amplifier or a speaker can process. The analog audio signal is presented as voice or sound by stereo speakers(not shown).
The NTSC encoder 180 converts the digital video data from the video decoder 150 into a luminance signal Y and a color difference signal C which can be displayed on a related art TV or a monitor. The luminance signal Y and the color difference signal C can be displayed by a CRT.
The microcomputer 200 controls operation of the digital TV receiver. And, programs and OSD information required for controlling the microcomputer 200 are stored in the ROM(Read Only Memory) 210, and temporary information required for the microcomputer control operation is stored in the RAM 220(Random Access Memory). That is, the microcomputer 200 processes the program specific information signal stream from the TP parser 130 and provides a program specific information data to the OSD processor 190 in response to control signals provided through a user input device 230, such as a remote controller or a key pad. Though OSD information is stored in the ROM 210, when a control signal is provided from the input device, the microcomputer 200 draws out OSD information corresponding to the control signal from the ROM 210 and provides it to the OSD processor 190. The OSD processor 190 converts the OSD information transmitted by the microcomputer 200 into a video signal that the NTSC encoder 180 can process. The switch unit 160 selects the OSD information converted into the video signal at the OSD processor 190 and the video signal converted at the video decoder 150 and provides the selection to the NTSC encoder 180. If no OSD information is provided according to the user input device, the switch unit 160 provides the video signal provided from the video decoder 150 to the NTSC encoder 180. And, if the OSD information is provided according to the user input device, the switch unit 160 provides the OSD information provided from the OSD processor 190 to the NTSC encoder 180.
However, the related art digital TV receiver can not receive an analog broadcasting signal, and the related art analog TV receiver can not receive a digital broadcasting signal. Therefore, if the user intends to watch both the analog broadcasting signal and the digital broadcasting signal, the user must provide two separate TV receivers, which is a substantial burden to the user.
Accordingly, the present invention is directed to a combined TV receiver which can receive and process an analog broadcasting signal as well as a digital broadcasting signal that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the digital/analog TV receiver includes a controller for determining a channel of user""s selection of being of a digital broadcasting or an analog broadcasting, and generating a station selection data on the channel and a control signal pertinent to the determination, a tuner for receiving the station selection data and tuning to a broadcasting signal pertinent to the channel out of signals received through an antenna, an IF switch unit for selecting a direction of forwarding the broadcasting signal tuned at the tuner in response to the control signal, an analog broadcasting processor for demodulating the broadcasting signal selected at the IF switch unit into an audio signal and a video signal, a digital broadcasting processor for decoding the broadcasting signal selected at the IF switch unit into digital broadcasting information, and an AGC(auto-gain controller) for receiving a gain signal either from the analog broadcasting processor or from the digital broadcasting processor and adjusting a signal gain of the broadcasting signal tuned at the tuner.
It is foreseen that the digital TV broadcasting systems will use channels the present analog broadcasting systems do not use, frequently. Therefore, the digital TV broadcasting signals can be received by an existing analog TV antenna. Moreover, an output frequency band of a digital tuner is also similar to an output frequency band of a tuner of an existing analog TV receiver.
However, a digital TV broadcasting signal has program specific information in addition to video and audio information. The program specific information allows a digital TV receiver to provide more information than an analog TV receiver. The present invention utilizes the very feature of frequency common use between a digital TV receiver and an analog TV receiver and the distinctive feature of the digital TV receiver of having the program specific information, for providing a combined TV receiver which can receive and process both the analog broadcasting signal and the digital broadcasting signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.